Building a large, half round wood frame

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Old 02-05-10, 10:21 AM
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Building a large, half round wood frame

Hi all,

I am looking to build a large stained glass window insert. The window is a 1/2 round arch just under 6' diameter (so about 6'x3'). Due to stained glasses inherent weaknesses (all the joints) I need a very sturdy frame for this. I plan to build one using plywood and solid strips.

My thoughts are as follows:

First, with 1/2" plywood, I would cut two identical round strips 1.5 inches high. I have done this in the past for molding by nailing a 1x4 at the center point of my plywood. This acts as a fulcrum and spins a perfect circle around my plywood. I attached a router to the other end of the 1x4 - sort of like a giant protractor. My pieces would then be rounded, 1/2 thick and 1.5 inchs high.

So, now I glue them together making them an inch thick. They should be strong enough that they keep their circular shape (right?) since the plywood on edge is pretty strong.

Then, I would glue a 1/4 inch strip of solid wood (1 inch wide) along the bend on top. This should give me left/right stability so that the piece doesnt torque/twist?

Then, I would use standard joining rabbitting to join to the straight 6' piece on the bottom.

Would this be strong as a frame? My concerns are:

1) It wouldnt be as solid as I expect.
2) Can I glue to the end grain of plywood as I would be trying to do?

I could decide to, instead of doing this as a half round, do it as two quarter rounds. So, same technique except I would have two smaller pieces instead of one larger one which Im assuming would be stronger. If I went down this path, I MAY consider even hinging them and make them like shutters that open - any thoughts on that?

Well, thanks so much for your time.
 
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Old 02-05-10, 04:11 PM
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How thick it the glass? Do you need the light to pass through it or can you use a backing?

I would go to a local glass shop for advice or look in a church.

Edit: I just thought of something. Can stained glass be tempered? Will that strengthen it?
 
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Old 02-05-10, 05:30 PM
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I'm not sure I understand what you are doing. From what I understand, stained glass panels do not get attached to the window frame, they sit in the frame and have a molding that holds them in place just like a regular piece of glass.

Stained glass panels are a network of lead strips soldered together that hold the glass between them. The lead is soft so when panels are large they tend to bow and sag. To hold panels like that up, small iron bars are soldered to the lead caming to add stiffness.
 
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Old 02-05-10, 05:34 PM
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Originally Posted by Pulpo View Post
Edit: I just thought of something. Can stained glass be tempered? Will that strengthen it?
Stained glass cannot be tempered. You would not be able to cut it. The pieces are also already fairly small and it wouldn't make any sense to do so.
 
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Old 02-06-10, 07:26 AM
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Ive spoken to a number of stained glass experts. Because of the size and design of my piece, they assure me that in addition to the reinforcement of the lead caming with rebar, a firm outside frame of wood or metal is neccessary. In fact, they "insisted" that the rebar that is soldered across must be notched into the frame. Since I cant work with metal (and dont want to pay $400) to have one made, wood is my better option.

Essentially, I think regardless of what I am putting inside the frame, I am looking to build a nice firm half-round (or two quarter-round) frames.

Im just not sure of the best construction method. What I outlined is my best guess at how to do it.
 
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Old 02-07-10, 04:34 PM
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The following link shows a photo page of the way I recently did the trim for a half round window in our house. You might get some ideas on how to construct yours by looking at the method that I used to fasten the frame pieces.

Hope this helps
Garry

Curved top window trim construction



 
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Old 02-07-10, 08:58 PM
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Gary,

What a great bunch of images for your process - and your moldings look great.

Its funny. I also made my own molding for my half round and used basically the same process with the router. I made all of my other moldings fluted and I couldnt find a fluted arch to match.

The difference is that I used a 4x8 MDF panel so I didnt miter together the pieces in the rough outline of a half circle as you did. My final modling was to be painted to match all my other moldings so I didnt need any grain.

I envisioned a similar process for this frame but, as I said using plywood for my half circle and then reinforcing on top.

I didnt even think of mitering a number of pieces together and then cutting it out.

So, now I just have to figure out what is easier/stronger/better. Plywood with a couple of 1/4 pine or oak strips on top to stop any torque, or mitering peices together as you did.

It will be painted white, so I dont need a grain.

Any thoughts?
 
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Old 02-07-10, 09:03 PM
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I just realized that you didnt glue - only pocket screws (I guess it wuold be useless to add glue to two end grains matching up - and as moldings - you didnt really need any strength.

I guess If I mitered, I would need to cut finger joints for gluing.

Uggg.
 
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Old 02-08-10, 07:05 AM
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Originally Posted by rmathome View Post
Gary,

What a great bunch of images for your process - and your moldings look great.
..
..
So, now I just have to figure out what is easier/stronger/better. Plywood with a couple of 1/4 pine or oak strips on top to stop any torque, or mitering peices together as you did.

It will be painted white, so I dont need a grain.

Any thoughts?
If I needed to rely on glue for a frame, I would likely use either a spline for each joint which would be fairly easy.
I used the spline method on this project on this page
Custom made Arched Arbor and Bent Curved Rail Picket Fence made of White Cedar from the Upper Peninsula of Michigan
Or I would likely use loose tenons (cut with my Festool Domino) in which case the tenons would be hidden.
I used both the spline method and the loose tenon method on this photo page
Custom made Solid Ash and Curly Yellow Birch Interior Doors

Good Luck
Garry
 
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